wouldn't surprise me if its tide pooling but thinks the water column is the tide itself depending on flow.
Fromias tend to run out of food in aquariums and starve, usually the response to this in the wild is to enter a different tide pool the moment the water raises a bit where the food is more present (this is what our aquariums are like to them, just octopus and sally lightfoot crabs don't wait for tides they traverse a bit on land),
Only way to confirm feeding behavior is if the stomache is out, but typically fromia is going to move from one feeding spot to the next, so if it isn't detecting food and moving to it (or maybe detecting it behind the over flow and waiting for the 'tide' to raise enough to crawl back there) it's probably trying to leave.